As is known, any broadcast program transmitting system stores the broadcast content data in a video server apparatus, plays back in accordance with the instructions coming from an automatic program control apparatus (APC) and executes an on-air. Before the programs are broadcast from the broadcasting station. In such an on-air process, the programs are usually confirmed in accordance with the on-air sequence.
The image quality has greatly increased, from high-vision level (3K×1K) to full high-vision level (4K×2K), and hence to super high-vision level (8K×4K). In addition, the broadcast content data has increased in volume, from the terrestrial broadcast level to the broadcasting satellite (BS) level and hence to the communication satellite (CS) level, and are broadcast in ever increasing channels. In order to store these content data, the video server required having a very large storage capacity and must distribute the programs to many channels. Therefore, the video server should have high data processing ability and should include not a single function, but a plurality of function modules that perform different functions.
In such an apparatus including a plurality of function modules, the function modules required that connecting to a high-speed bus, thereby transmitting and receiving a great amount of data. Particularly, video data should be transmitted and received, in real time of frame level. The high-speed bus used to transmit and receive data between substrates in a great amount is not a synchronous bus, but a versatile, high-speed asynchronous bus, in some cases.
In the multi-CPU configuration described above, the CPUs required playing back data within a predetermined time, in synchronism with control of frame units. Hence, a video server can ensure the quality of images played back if the video server has any means for synchronization among the CPUs. Timers may be used to make the CPUs operate in unison. In this case, however, a method of making synchronizing the timers must be performed. This will render the inter-CPU process complicated. High-precision timers may be incorporated in the processor, respectively, and the CPUs may refer to the time any timer measures. The use of high-precision timers, however, will raise the apparatus cost.
Even if timers are provided for the CPUs, respectively, and are synchronized at high precision, any video data played back will not improve in quality unless means for detecting failures in one-frame control is used to recover the failure in, for GOP. Without a means for notifying that failures that cannot be recovered, the switching to any redundancy system cannot be achieved. It is difficult to provide a video data playback apparatus capable of ensuring the quality of the images played back.